Resin infused fiber composite materials are being used increasingly in a variety of diverse industries, such as automotive, aircraft, and wind-energy, in part, because of their low weight and high strength properties. Adapting to changes in AFP equipment designs, tape and tow thickness requirements, new resin types, variations in impregnation levels, spread tows, out-of-autoclave (OOA) technologies and the application of thermoplastics requires new devices and methods for handling materials. New processing methods might employ in situ heating/consolidation of the precision-slit tape at the spool head/tooling calling for improved equipment.
Composite material machine manufacturers have been working to reduce the minimum tow length by reducing the size of the parts in the head. With the roller diameters all converging to about 2 inches, and the cutter locations as close as they can be, the minimum tow length is about 4 inches for all but specialty machines. Fiber placement machine capability is limited by minimum tow length, i.e. the distance from the cutters to where the roller meets the tool (usually about 4 inches). Additionally, incorrect starting paths for tows have not been corrected and tows are sometimes not laid accurately at the start of a course as they are pushed out of the head around the roller while the roller is moved onto the tool. The machines depend on the tows maintaining their shape and location in space as they are pushed out of the head past a curved guide before reaching the roller. Depending on many factors including tow width and stiffness, temperature and resulting resin viscosity, and trajectory and speed of the head motion, the tows can start off-course. In this case, they may become wrinkled as the head follows the intended path and the tows are forced to follow from a non-aligned starting path thereby affecting quality and length of the fiber tows.
A typical prepreg AFP system uses material that comprises a bed of fibers that have been pre-impregnated with uncured resin then slit to tape of the required width. The material is spooled as it is slit, then the spools are stored in freezers until ready for use to avoid advancing the cure state of the resin. Prepregs, comprising a fiber arrangement impregnated with curable thermosetting resin are widely used in the preparation of composite materials that allow careful control of the fiber and resin quantities and provide flexibility in the shapes they can adopt. However, these systems do not permit control of the fiber placement head roller, also referred to as the compaction roller, to provide more accurate placement of individual tows.
It would therefore be desirable to provide an improved system that permits control of tows as they pass around the compaction roller. In addition, it would be desirable for the system to facilitate adjustable and selectable vacuum assistance to the compaction roller to hold the one or more fiber tows against the roller during layup of the infused fiber tows for formation of complex composite components. The desired results create an AFP system that is more functional, is applied to a wider range of part geometries, leads to higher quality, and allows for short length fiber placement.